Though it is true that these indoor plants are carefree and thrive on neglect, they will grow better if they are fertilized on a regular basis during the growing season.

You can choose between slow release, granular formulas and soluble types that are added as needed.

Generally, I use a soluble fertilizer about every three to four weeks when the plants are actively growing. This is mostly from the spring to early or mid-fall. This assumes that the room temperature is at least 60 degrees Fahrenheit. During the plant’s resting period, fertilizer should never be
used. Normally, I use about half the rate that is recommended on the package.

For the most part, the soluble fertilizers work fine since they can be used on an as needed basis. The fertilizer can be added to the water you would normally use when you water the plant. Add enough solution to the pot so that the potting soil becomes thoroughly moist and the liquid runs out the drainage holes in the bottom of the pot. This method helps to prevent build-up of soluble salts.

There are any number of special fertilizers especially formulated for cacti and succulents. In most cases, the word cactus or cacti will appear in the name.

One such brand is Cactus Juice. Some gardeners swear by the Dyna-Gro brand of soluble fertilizers. This are available from companies that sell special hydroponics products.

Cactus plants need fertilizers that are low in nitrogen. Nitrogen is the first number listed in a formula. Fertilizer labels list the ratios of the three main ingredients needed for plant growth, which are nitrogen, phosphorus, and potassium. The important thing here is to pay attention to the ratios so that the first number—the nitrogen—will not be higher than the other two numbers that are listed.

In the United Kingdom, for example one can buy 8-34-32, and 3-7-7 specially formulated for cactus. Another suitable one that is available has a formulation of 15-15-30. The Schulz brand has a formulation of 2-7-7. It is helpful if the fertilizer also contains trace elements.

If you choose to use a general, all purpose soluble indoor plant food, just be sure it is low nitrogen.